Muffler



g- 3, 1965 w. H. POWERS 3,198,284

MUFFLER Filed Sept. 6. 1961 2 Sheets-Sheet 1 8" 1965 w.- H. POWERS 3,198,284

MUFFLER Filed Sept. 6. 1961 2 Sheets-Sheet 2 IN VEN TOR.

United States Patent This invention relates to devices for attenuating or removing sound from the exhaust gases of internal combustion engines and, in particular, concerns a compact mufiier of a type that may be used to silence the exhaust 'of engines used with lawn mowers.

It is an object of the invention to provide a highly effective silencing unit which can be manufactured at a reasonable cost.

It is also an object of the invention to provide a lawn mower mutiler which is extremely compact and of a shape such that it fits well into the space available for it on typical power lawn mowers.

The invention accomplishes the foregoing and other objects by means of a construction which is box-shaped as distinguished from the more frequently used cylindrical shape. The interior of the box is provided with stampings which fit together to provide a sinuous passage for gas flow through the muflier unit. The space within the muflier is divided into chambers by means of the stampings and these act in conjunction with the sinuous path to remove the objectionable noises from the gas traveling through the rnufiler box.

The invention is illustrated in its presently preferred form in the accompanying drawings in which:

FIGURE 1 is a plan view taken from the top of the muffler; 7

FIGURE 2 is a transverse sectional view of the muflier taken along the line 2-2 of FIGURE 1 in the direction of the arrows;

FIGURE 3 is a longitudinal sectional view of the rnufiler taken along the line 3-3 of FIGURE 1 in the direction of the arrows;

FIGURE 4 is a longitudinal sectional view of the mufiier taken along the line 4-4 of FIGURE 3 in the direction of the arrows;

FIGURE 5 is a detail plan view of one of the inner stampings;

FIGURE 6 is a side view of the stamping shown in FIGURE 5 taken in the direction indicated by the arrow FIGURE 7 is another side view of the stamping shown in FIGURE 5 taken in the direction indicated by the arrow 7;

FIGURE 8 is a sectional view, partly broken away of a portion of the structure shown in FIGURE 3 and shows a modification wherein an additional chamber is provided in the mufiler box; and

FIGURE 9 is a cross-sectional segment of an outer portion of the muffler shell showing a modified form of the abutting rims which function as snap-on locking devices.

The muffler construction shown in the drawings consists of two principal parts. The first of these parts is the casing or shell forming a rectangular box 1. The second of these parts is an insert 3 inside of the box which provides the passage to conduct exhaust gas from the mufiler inlet generally designated 5 to the mufiler outlet generally designated 7. The insert 3 also acts with the box 1 to provide chambers to attenuate sound in the exhaust gas within the muffler. In particular, the insert 3 provides a resonator chamber 9 and a spit chamber 11, as well as an inlet chamber 13.

The box 1 comprises a pair of pan-shaped sheet metal sections and 16, one of which may be provided adjacent its open side with a rim 17 and the other with a rim 19. These sections are fitted together, rim to rim, and

the rim 19 is crimped around the rim 17 to tightly secure the two sections together to form a substantially gas-tight box. It is noted that variations in the structure of rims 17 and 1E could be employed which would allow the sections to be snapped or forced together with suflicient force to prevent their separating under operating conditions. Such a structure is shown by way of example in FIGURE 9 wherein the rims of sections 15 and 16 are formed into mating locking edges 18 and 21 respectively.

A gas inlet port 21 extends through a pad-like embossment 23 which is formed in a corner of box section 15 and projects slightly beyond the outside of the box as shown in FIGURE 2 to provide a fiat gasket engaging surface. Both sections 15 and 16 of the box have openings 25 formed therein and may frictionally tightly receive tubes 27 extending between the outer surfaces of embossment 23 and section 16 for receiving bolts 28 having threaded ends adapted for threaded securement in an engine exhaust manifold section. Tubes 27 serve to prevent over-tightening of the bolts 23 against the outersurfact of section 16 and also act to reinforce the box at the inlet section adjacent inlet 21 which is subjected to the forces associated with the rapid and high energy pulses of gas entering the mufiler. Bolts 28 also assist in clamp ing sections 15 and 16 together.

The box 1 is provided with an outlet pipe 31 which in the embodiment illustrated is of substantial length so that it may be capable of directing the exhaust gases leaving the muffler to a point underneath the lawn mower blade shroud. The pipe 31 is secured to the box by spot welding to the mating arcuate rim portions 33 and 35 formed in the rims of top and bottom sections 16 and 15 respectively, and curved appropriately to lit the contour of the outlet pipe 31. By welding pipe 31 to the sections 15 and 16, these sections are further tightly secured together. Pipe 31 may be plugged at its outer end and perforated along its sides should it be desired to diffuse the exhaust gas stream. As will be pointed out presently, the tube 31 is located so that it will be in precise alignment with the outlet end 32 of the gas passage provided by the insert 3.

The insert 3 is made up of two inner sections 36 and 37 which are preferably stamped, and which are spot welded together at their flat portions back-to-back as at 38 as seen best in FIGURES 2 and 3. Section 36 is provided with end legs 39 and 4e, and section 37 with end legs 41 and 42. Legs 4% and 42 extend diagonally across the box 1 between the sides 43 and 44 respectively of sections 16 and 15 to provide the inlet chamber 13 communicating with inlet 5 and the internal portions of the mufiier in a manner hereinafter described. The legs of these sections engage sides 43 and 44 with sufiicient force to prevent rattling of insert 3 within the box 1.

Leg 411 is provided with a large opening 45 as shown in FIGURES 6 and 7 which permits gas and sound waves in the inlet chamber 13 to flow into the dead end or resonator chamber 9 that is formed between the shell section 16 and the inner section 36. It will be recognized that gases which enter the chamber 9 through opening 45 must leave by the same opening since there is no other exit. Section 36 is provided with a sinuous formation generally indicated 51 of semi-circular cross-section and preferably stamped therein simultaneously with the stamping of section 36. This formation forms a tri-fiow gas path that consists of an inlet portion 53, an intermediate portion 55, and an outlet portion 57. Portions 53 and 55 are joined by a U-portion 59 while the portions 55 and 57 are joined by the U-portion 61. The outlet portion 57 connects with a right angle outlet portion 63 which 0 is in alignment with the outlet pipe 31 previously is cent section 36 and welded thereto to form a continuous sinuous gas passage 65 as shown in FIGURES 2, 3, 6, and 7. Section 37 is perforated along the sinuous formation comprising the portions 53, 55 and 57, as seen at 67, to connect passage 65 with chamber 11. These perforations permit the gas passing through passage 65 to flow into the chamber 11. In so doing, the gas is further relieved of energy and heat, and the roughness caused by the high energy exhaust pulsations is considerably reduced. Chamber 11 thereby further acts as a relatively large spit chamber for silencing higher frequency noise.

It will be seen that there is a small unused chamber 69 between the legs 39 and 41 of the insert sections 36 and 37 respectively, and the back wall 71 of the box. This chamber with its present volume could be used, if desired, to further deaden the exhaust sound by providing perforations in one or the other of legs 39 and 41. Moreover, chamber 69 can also be made larger and utilized as an additional resonator chamber to be compounded with the resonator chamber 9. This could be done .by forming a right angle spacing tab 73, as shown in FIGURE 8, in the leg 39 of section 36 to engage the back wall 7 1 of the box to space the insert 3 properly with respect thereto. This larger chamber will then have suflicient volume to silence some of the heavier notes. Alternatively, the chamber could be used as a spit chamber by forming a plurality of perforations in the legs 39 of the lower section 36.

In the operation of the mother, gas will enter therein through the inlet port 21 and flow into the inlet chamber 13. This will be accompanied by some expansion and cooling of the gas resulting in silencing thereof. It will then flow into and through the gas passage 65 to the outlet pipe 3 1. During the course of this flow, the .perfonations in the section 37 permit sound waves to expand into the spit chamber 11, thus silencing the scratchy, high frequency noises. Gas in the inlet chamber 13 and the sound waves of longer wave length can expand through the open-ing 45 into the dead end chamber 9 and be silenced or attenuated therein.

It will be recognized that the invention provides an inexpensive, compact, and readily manufactured mufller which uses a unique principle of construction to provide various sound attenuating techniques. While the construction illustrated is intended for use principally with lawn mower motors, it is clear that the same principles can be embodied in mufflers for other uses, such as automobiles, The latter use is of some significance at the present time because the mufiier construction illustrated herein can be made quite fiat and thus can be readily adapted to the cramped spaces available for it in modern low slung automobiles.

I claim:

1. A lawn mower rnufller comprising a relatively small box-like casing, means in said casing providing an inlet chamber, means in said casing providing a resonator chamber, means in said casing providing a spit chamber, and means in said casing providing a tri-ilow passage separating the resonator chamber from the spit chamber and having communication with the spit chamber and opening into the inlet chamber.

2. The invention set forth in claim 1 wherein substantially the entire length of the tri-fiow passages communi-' cates with said spit chamber.

3. In a mother, a casing, a gas fiowpassage member in the casing comprising a pair of stampings secured together, one of said stampings being flat, the other of said stampings being formed to provide gas passages, said stampings and said casing defining sound attenuating chambers in said casing and through which exhaust gases cannot flow, one of said stampings being perfiorated, said last mentioned stamping having transverse legs thereon to space the perforated section from the wall of the casing, the other side of the insert being imperforate, said other side having legs engaging the wall of the casing and acting with the first mentioned legs to form a diagonal partition acting with the wall of the casing to provide a chamber, said diagonal partition having an opening providing the only inlet and outlet for said chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,682,316 8/28 Williams l8l57 X 1,756,916 4/30 Stranahan l81-49 1,822,990 9/31 Gorsline l 8148 X 2,182,945 12/39 Gunn l8l 54 2,484,826 1 0/49 Harley 1'81-49 X 2,727,584 12/55 Marx 1 8l--57 2,902,109 9/59 Burgess et al. 181-53 2,908,344- 10/59 Maruo l8l59 2,922,485 1/ 6O Muller 181--54 2,934,161 4/60 Powers l8l53 3,125,182 3/64 Earley 181-53 LEO SMILOW, Primary Examiner.

CHARLES W. ROBINSON, Examiner. 

1. A LAWN MOWER MUFFLER COMPRISING A RELATIVELY SMALL BOX-LIKE CASING, MEANS IN SAID CASING PROVIDING AN INLET CHAMBER, MEANS IN SAID CASING PROVIDING A RESONATOR CHAMBER, MEANS IN SAID CASING PROVIDING A SPIT CHAMBER AND MEANS IN SAID CASING PROVIDING A TRI-FLOW PASSAGE SEPARATING THE RESONATOR CHAMBER FROM THE SPIT CHAMBER AND HAVING COMMUNICATION WITH THE SPIT CHAMBER AND OPENING INTO THE INLET CHAMBER. 